Effects of long and short heat treatments on the properties of Nb3Sn composite strands

摘要

The development of high J(sub c) multifilamentary Nb(sub 3)Sn strands with low magnetization is of relevance in many technological fields, including that of high field accelerator magnets. Whereas the J(sub c) of a Nb(sub 3)Sn strand made with the Internal Tin technology depends substantially on design and composition, the heat treatment (HT) leaves some margin for improvement. However, the thermal cycle must also be adequate in preventing Sn leaks, which have become a relevant issue in high Sn strand designs. To study HT effects on I(sub c), n-value, RRR, magnetization and effective filament diameter, a long and a short thermal cycles were applied to five different Nb(sub 3)Sn strand designs. The Cu-Sn diffusion behavior was monitored at various stages of both cycles. Next, low temperature steps were applied to bent cables in order to check for Sn leaks.